In general, artificial breast prostheses are used in reconstructive plastic surgery for a breast when breast loss occurs due to diseases or accidents and in cosmetic surgery for a malformed breast. In terms of anatomy, artificial breast prostheses are also used for the substitution of organs or tissues.
Artificial breast prostheses are products in which a filling material, such as saline, hydro-gel, and silicone gel, is filled in an envelope formed of silicone that is implantable to an organ (hereinafter referred to as a “shell”). These artificial breast prostheses may be classified into round products and water drop shaped products according to the shape of a product, and may be classified into smooth products and textured products according to the surface conditions of a product. More particularly, the artificial breast prostheses will be described in brief as follows.
A saline filled artificial breast prosthesis is configured such that saline is injected or is injectable into a shell formed of silicone (more particularly, the shell being formed of polyorganosiloxane, such as polydimethylsiloxane or polydiphenylsiloxane). The saline filled artificial breast prosthesis has a structure consisting of a silicone shell and a valve.
Although the saline filled artificial breast prosthesis ensures safety of a user even if the filling material leaks into the human body after rupture of the shell as a result of using sterilized saline as the filling material, and is easy to change the volume of a breast by adjusting the injection amount of saline, the saline filled artificial breast prosthesis is significantly deteriorated to the touch after surgery as compared to other artificial breast prostheses and the shell thereof has inferior durability.
A hydro-gel filled artificial breast prosthesis is configured such that hydro-gel composed of monosaccharide and polysaccharides is filled within the same shell as that used in the above described saline filled artificial breast prosthesis. The hydro-gel filled artificial breast prosthesis is a product developed based on the principle that the filling material can be absorbed into and excreted from the human body even if the filling material leaks into the human body due to rupture of the shell.
However, in the case of the hydro-gel filled artificial breast prosthesis, safety with respect to long term use has not been established, volume change depending on the lapse of time and occurrence of wrinkles may increase after the artificial breast prosthesis is inserted into the human body, and feeling is unnatural as compared to a silicone gel filled artificial breast prosthesis. At present, the above described hydro-gel filled artificial breast prosthesis are not distributed in the market on the basis of the year 2000 due to problems in relation to the proof of safety.
A silicone gel filled artificial breast prosthesis is configured such that silicone gel having an appropriate viscosity is filled in a shell. The silicone gel filled artificial breast prosthesis has very superior product durability and more pleasant texture than the saline filled artificial breast prosthesis, and owing to these advantages, achieves a dominant position in the market. Although the Food and Drug Administration of the United States of America had imposed limitations on use of the silicone gel filled artificial breast prosthesis due to problems in relation to the proof of safety thereof, the use of the silicone gel filled artificial breast prosthesis was again allowed officially in the year 2006.
The silicone gel filled artificial breast prosthesis has been developed in the order of a first generation prosthesis, a second generation prosthesis, and a third generation prosthesis. This development history will be described in detail as follows.
The first generation silicone gel filled artificial breast prosthesis is a product sold from the middle of the 1960s to the middle of the 1970s, and was initially developed in the year 1961 by Cronin and Gerow. The first generation silicone gel filled artificial breast prosthesis can be represented in brief by the use of a thick shell, a smooth surface type, and silicone gel of a high viscosity. This prosthesis has caused gel bleed and capsular contracture, but a rupture speed thereof was relatively low due to the use of the thick shell.
The second generation silicone gel filled artificial breast prosthesis is a product sold from the middle of the 1970s to the middle of the 1980s, and includes a thin shell and a silicone gel filling material of a low viscosity, for the sake of smoother texture. This prosthesis is characterized by a similar gel bleed rate, higher rupture occurrence, and lower capsular contracture as compared to the first generation prosthesis.
The third generation silicone gel filled artificial breast prosthesis is a product sold from the middle of the 1980s to the present, and includes a gel bleed barrier layer to prevent gel bleed. The third generation silicone gel filled artificial breast prosthesis includes a thicker shell and silicone gel of a higher viscosity as compared to the second generation prosthesis. In addition, a product having a rough surface has been developed, in order to reduce capsular contracture.
The above described artificial breast prosthesis commonly include a shell, a bonding portion (hereinafter referred to as a “patch”), and a filling material.
Considering first the shell, most shells have been produced via a dipping method and have a limit in durability (in particular, against fatigue failure). Basically, the shell produced via a dipping method exhibits thickness deviation due to gravity, and this thickness deviation causes a portion of the shell to be relatively weak to stress.
The bonding portion (i.e. the patch) is formed using a patch to be bonded (i.e. a material to be placed over the shell), and a bonding material. In production of conventional artificial breast prostheses, the patch, which constitutes the bonding portion, has been formed of a material having the same thickness and same physical properties as the shell.
This is because although it is necessary to produce a multilayered patch which includes a barrier layer for preventing leakage of low molecular weight silicone in order to prevent strength deterioration of the patch, production of the multilayered thin film patch having a smaller thickness than the shell is commercially very difficult.
More specifically, as shown in FIGS. 1 and 2, in the case where a patch 6 having the same thickness as that of shells 5 and 7 (the average thickness of which is in a range of 500 μm to 800 μm) is used, bonding portions 8a and 8b are very thick and have lower expansibility. Further, stress concentration may occur due to a difference in physical properties at a boundary point between the shell and the bonding portion, which deteriorates durability against fatigue. As a result, rupture of the artificial breast prosthesis has very high occurrence frequency around the patch as known from clinical results.